Speed control system for centrifugals



May 8, 1951 R. .1. HUSER rrAL 2,551,838

SPEED CONTROL SYSTEM FOBl CENTRIFUGALS Filed June 2l, 1947 2Sheets-Sheet 1 INVENTORS Afc//mra J /rmrf ,444W vzw May 8, 1951 R. .1.HusER Er AL 2,551,838

SPEED CONTROL SYSTEM FOR CENTRIFUGALS Filed June 21, 1947 2 Sheets-Sheet2 5 SEC.

OFF ON l0 SEC MINUTES r P72 PT/ 5 zoo RPM START 45o sHTFr Low To HTGH|500 coAsTlNG. STARTS REGEN. BRAKE STAR-rs n OFF MECHANJCAL BRAKE ONMACHINE STOFS Ma/M HTTOR/YEYJ Patented May 8, 1951 UNITE-D STATES PATENTOFFICE .SPEED CONTROL SYSTEM FOR 'CENTRIFUGAL'S ApplicatonfJuneZl, 1947,Serial No. 756,307

4 Claims.

'This invention relates to a system or apparaitus for the control ofcentrifugal apparatus, particularly of the type used 1in sugarreiineries, and is especially concerned with the control fof the speedof the centriugals used therein.

In sugar centrifugals, the loaded basket must be accelerated Ato runninglspeed in an .extremely short period, the complete cycle being .as short:as two minutes and less. `When the basket :is iconnected directly to anVelectric motor, a very high load is placed on'the -motordue `to thehigh acceleration required of the 'loaded basket. If a iiui'd couplingis interposed between the electric driving motor and the basket, a veryhigh-loadfalso `is placed on the motor yduring acceleration unless somespecial arrangement of the fluid coupling is employed. Some of said Huidcoupling :special arrangements do not transmit power through thecoupling in the most efficient Vmanner throughout the acceleration ofthe basket. Standard :electric motors -will not function properly lunderthe aforementioned high load conditions because there is insufficienttime for fthe 'motor to cool after the completion of each cycle andbefore the next cycle is started, 'the cycles -off operation `-nor imally being frequently repeated. Consequently, it has been the generalpractice -to use specially designed and constructed expensive electric-motors for individually driven electrically operated sugarcentrifugals.

When alternating current motors are used, vthe speed of the motor islgoverned -by the construction of the motor, number 'of poles, and vthefrequency of the power supply. For example, standard alternating currentv60-cycle motors have rated or vsynchronous speeds of i800 and 1200 R.P. M. for 4 and v6 pole motors, respectively, with full load runningspeeds slightly thereunder. Frequently it has been found that sugar willbe undertreated when subjected to a centrifuging speed of near 1200 R.P. M. only, whereas the sugar will be overtreated at a speed near 1800R. P. M. When the sugar is overtreated, it may be packed so hard as tocaused'iiliculty inthe discharging operation.

One of Athe objects of the invention is to provide a control apparatuswhereby standard electric motors can be employed without the necessityof using specially built motors l'to withstand the heavy loadrequirements of :acceleration in sugar and similar type centrluga'ls.

Another of the object `of the invention is `to provide a system andapparatus wherein centrifugal speeds below vthe rated speed "of anralternating current driving motor can lbe attained, as fde- .2 sired,to suit the processing requirements of particular materials.

A Afurther Vobject vris to save power, increase motor operatingefficiency, and avoid overloading of the rmotor .in the use -of heavymotor-driven centrifugal machines.

One of the features of the invention in aidirect connected `drive is the-use of a 'standard electric `eration `of heavy motor-driven`centrifugal imachines. Power is supplied to the motor at the beginningof the acceleration, and, at the end of .a predetermined time :period.permitting the centrifugal -to reach the desired speed below the normalrunning Ispeed `of the motor, power is cut off Vto the motor andthecentrifugal is allowed to coast under its own momentum until thepurging or .separation of materials, washing, or l-orther operations arecompleted. Thus, the centrifugal can -be voperated at almost any`desired speed below :the operating speed of the electric motor depending upon the time the accelerating power iis supplied to fthe motor.

'The Iaccelerating power is applied to the mo'- tor only for a shorttime :during the cycle, and therefore the motor will have an opportunityto cool between intervals of heavy power applica,- tion. In addition tosaid opportunity to cool between power applications, the cooling rate:of the motor will `be higher dueto rotation during the coasting periodas compared with the cooling rate of a motor at standstill.

In accordance with one aspect of the invention, the time of applicationo'f power for acceleration 'in a direct-connected electric-driven`centrifugal can be governed by a timer K'arrangement which operates at'the `end of `a predetermined time to interrupt the supplygof power 'tothe lelectric drive motor or to 'interrupt the driving action thereofbefore the potential or running speed of the Velectric motor is reachedby the :centrifugal basket. The predetermined time is adjustablyselectable so that the centrifugal can be operated to reach any desiredoperating speed.

When a hydraulic coupling for #fluid drive is used to connect the'electric motor with the .centrifugal basket, the system of the 'presentinvention vcan be applied so as to interrupt the 'flow 'of oil to thecoupling at a predetermined time after acceleration istarts, `and thusthe 'operating speed of the 4centrifugal basket can be made less thepotential or running speed of the driving motor or potential speed ofthe driving apparatus.

Another feature of the invention is the provision of a cycle controlarrangement wherein, in consequence of the movement of a single controldevice such as a starting button, a control timer and a process timerare started and these can time, when low and high speed motor windingsare employed, the shift from low to high speed windings to the drivemotor, the time of acceleration until power to the motor or fluid to acoupling is cut 01T, the time of coasting, application of regenerativebraking if used, application ofA the mechanical brake, and other desiredoperations.

vantages of the invention will become apparent from the followingdescription andl drawings which are merely exemplary.

In the drawings: i Fig. 1 is a schematicview partially in Sectio lof oneform of theinvention; i

Fig. 2 is a schematic wiring diagram of a icircuit that may beemployedin carrying out the invention.

-1 Fig. 3 is a diagrammatic View of the face of a control timer suitableVfor use in the circuit of Fig. 2.

Fig.`4 is a diagrammatic view of the face of a process timer that may beused in -the circuit of Fig. 2.

In the direct driven centrifugal of Fig. 1, elecl tric motor 2n drivessuspended rotatable gyratory basket 2l through shaft 2'2, the motorbeing directly connected to said shaft and basket. Brake vdrum 23 hasbraker bands 24, the brake bands being movable to grip brake drum 23 bymeans' of apparatus attached to bracket 25 as will be vdescribedhereafter, lthe bands being'hinged at bracket 26 to the machine frame ina well known manner.

As explained in detail in the copending application Serial No. 756,308filed June 21, 1947, the brake bands can be expanded or contractedlrela'- tive to the brake drum by means of an operating device such asthe torque motor 23 moving link 29, link 2S operating the brake applyingmechanism shown diagrammatically at 30. A torque motor is a motor whichrotates in a limited arc upon application of electric power thereto, thetorque motor having an arm connected to -the shaft thereof to which link29 can be fastened.

A hydraulic cylinder, as described in said afore-mentioned applicationSerial No. 756,308, also may be used to operate the brake applyingmechanism, as well as any other suitable apparatus. When a hydrauliccylinder is employed, the applications of pressure thereto may becontrolled by a solenoid.

As yan aid to the operator, ab tachometer 34 ofsome suitable descriptionmay be employed, said tachometer being connected to give an'indicationof the speed of the centrifugal basket.

One form of wiring diagram and controlV Circuit whichmay be used ,isv'shown in Fig. :Zasaid or distinguishing subscripts or letters.

vswitches operable by the process and control 'I'hese and other objects,features, andad- -15 and high speed windings.

circuit omitting such features as the basket wash water control, thesyrup separator control, etc. As is well known in the art, a solenoidcan be used to operate a plunger or other mechanism connectedmechanically to any number of switch operators. In the accompanyingdrawing, the mechanical connection is omitted in the interests ofclarity, the switches operated by a solenoid being given the samenumeral with appropriate The timers will be identified by the referencecharacters PT and CT, respectively, with distinguishving subscripts.

Power -is supplied from a three phase source of alternating current Ilmto the main driving motor 20 having separate connections for the lowPower for the control circuit is taken from mtransformer m2 to bus bars|03 and IBG of the` control apparatus. The control apparatus may belocated inthe control lbox indicated schematically` at SI in Fig. 1,suitable motor switches being located in the control boxv 32, and thestarting and resetV but-y tons being located at a convenient Apoint `3,3as desired. Itis evident that the control apparatus and control buttonsmay be grouped and placed as convenient. I

In order to start the basket centrifugal from rest, or to start theautomatic control and acceleration of the centrifugal after the baskethas been loaded and Yis revolving slowly, the start push button IID isdepressed which will energize starting relay solenoid I I I to closeholding switch IIIa around starting button IIJ, switch IIIa beingoperatively connected .with solenoid I I I.

Closing of the circuit to bus barsv m3 and IIIA rwill cause energizationof low speed solenoid I I2 which will close circuits through connectedcontacts II2c, II'Zd and IIZe to the low speed windings of drive motor20. The process timer, which will be described hereafter, will have itsclutch solenoid II3 energized and will have operating motor H4 thereofstarted, switch PTO, connected with the process timer operatingmechanism, -being normally closed at the beginning of the cycle.solenoid vI I5 energized and its control motor IIS started, switchcontact I I2a connected with solenoid I I2 having.v been closed uponenergization of solenoid II2 and switch C'Io being normally 4closed atthe beginning of the cycle. Ihe manner in which the timers operate theswitches will be described hereafter. .l In the drive motor 2l] shown, alow and high speed winding are used and the low speed winding isenergized first so that provision must be made to shift to the highspeed winding at the desired time. If, for example, the motor has arated high speed of 1800 R. P. M. andthe full rotation of the low speedwinding is 900 R. fast acceleration being desired, the timing of. therelay circuits may be arranged so that there will be a shift from thelow to the high speed winding of the driving motor when ,the drivingmotor reaches about 450 R. P. M., lthe exact speedof shift being amatter of choice,--motor characteristics, and other variable factors.Loading of the basket may be carried out before this shift, usually at aspeed of about 200 R. P. M., either while the basket is beingaccelerated on the low speed winding, or while the motor idlesand isjogged to about such a speed, through successive movements ,of startbutton I IIIand circuit @senseless .button '.09 .ibevre .Starting the.

The control timer will have its clutch actual :treating cycle. The.reset button is normally closed and only opened momentarily to permitthe circuit to reset. In the particular process'and control timers, aclutch connects the switch operating motor with the switch operators.When a motor is stopped, the switch operator will remain at its stoppedposition as long as the .clutch remains engaged. I1" the clutch isdisengaged, the switches will be returned to zero by suitable means. Theresistances |23 may be employed Vwith any suitable control forenergizing the low speed windings therethrough, so as to modify thetorque at very low speeds, where a very low speed of the centrifugal isrequired, such as for discharging between :successive running periods.

The aforementioned speed 'winding shift can be accomplished by thecontrol timer switch CTi being closed by the control timer after aVpredetermined interval folicwing the start of the cycle, the controltimer having been started at the beginning of the cycle by beingconnected across control bus wires m3, 104. Immediately after, or at thetime switch CT1 closes, switch GT2 is lset to be opened by the controltimer .so as to deenergize the low speed solenoid H2, 'contact H8bconnected to solenoid H8 having been opened at the beginning of thecycle 'because of energization of solenoid II 8, switch FTQ beingclosed. Opening of contact GT2 will allow high speed solenoid vI Il tobecome energized because GT2 deenergizes low speed solenoid H2 so thatswitch conta-ct H213 connected to solenoid H2 will close and completethe circuit to solenoid Ii l, normally open switch Contact IIa havingbeen closed when the start button was depressed. Energization of highspeed solenoid i I7 will 'close contacts H'Ic, Hld, Hic, HU and 'I'i'igto connect the high speed windings of main driving motor 29 to thesource of power, said solenoid being operatively connected to switchesIlle, d, e, f, g. Low speed switch contacts 112e, I IM. and H2eoperatively connected to solenoid 'I I2 were opened upon de-energizationof low speed :solenoid H2. upon deenergization of solenoid H2 and stopthe control timer motor H6, but the control timer will not reset itselfinasmuch as the clutch vsolenoid H .remains energized.

At the end of a predetermined time., which is 1' that necessary toaccelerate the driving motor and centrifugal to the desired operatingspeed, switch PTl of the process timer will be opened thereby andde-energize solenoid I l?, thus opening the operatively connected highspeed contacts H1c, II'Id, IIle, H-If and Ille, cutting citpower to thedrive motor and causing the driving motor to coast.

Brake cooling water solenoid I i9 was energized when yswitch C'I1 wasclosed by the control timer, switch H8a having `been previously closed,so as to open a valve supplying cooling water to the brake drum in amanner similar to that disclosed in the patent to Roberts, No. Re.22,686. Solenoid H9 will remain energized so as to continue the supplyof cooling water to the brake drum during the coasting operation becausesaid solenoid is shunted across switch PT1, solenoid I Il and switchcontact H212.

At the end of the predetermined coasting period, switch PTz is opened bythe process timer, which has continued to run, since the start of .thecycle so as to de-energize solenoid H8, which .in turn opens theconnected contact Ha to interrupt the supply of current to `brakecooling water Switch contact H2@ also will open solenoid H9 and thusshut the water supply valve for brake cooling. Normally closed fcontactH81), which was opened by the energized solenoid -I I8 at the beginningof the cycle, also will close and thus connect the low speed solenoid H2to the bus bars. Closing of contact -I I8b by de-energiza-tion vofsolenoid H8 will thus close the connected low `speed winding switchcontacts H2c, H2d and H2e to the source of power VI'IlI) so that thelmotor vwill be subjected to regenerative braking, switch -contact Illahaving closed upon de-energization of the high speed .solenoid III, itbeing noted that switch `GT2 was opened previously during theacceleration period.

At the .end of a short predetermined period suitable for theregenerative braking, switch CTg will be closed by the control timer,the control timer having been started again upon the beginning of theregenerative braking inasmuch as the energization of the low speedsolenoid H2 has caused switch contact I I2C. again to close. Closing ofswitch ICTs will energize solenoid 'I 2E, which will open connectedswitch contact I29a inthe low speed relay circuit and thus stop theregenerative braking. At the same time, switch contact |2017 operated bysolenoid |20 will be closed .and thus energize the brake motor solenoidI2I. Energization of solenoid IZI can be used to cause energization ofswitch contacts I2 la, I2Ib and I2Ic to energize the brake Vsettingtorque motor 28 or to energize a solenoid controlling the admission ofair to a :duid pressure operated brake cylinder as disclosed incopending application, Serial No. 756,308.

Thus, the machine is no longer subject to driving torque, and thefriction brake bands 24 are applied to the brake drum 23 so as to bringthe machine to rest.

After the centrifugal cornes to rest, other operations, as desired, maybe performed and the circuit reset for the next cycle by momentarilydepressing the reset button |09 which will reset both of the timers byde-energizing the clutches and thus permit the timers to return to zero.

Various types of timers may be used and various arrangements thereofmade. In the preferred form, a composite unit type, such as is known asthe Multiex, and diagrammatically illustrated in Figs. 3 and 4, can beemployed, it being understood that separate timers or time delayswitches may be used for each of the timing functions. The Multiflextimer is well known and does not need to be described in detail exceptto point out that in the Yform shown in Fig. 3, four individually timedswitches are available, and in Fig. 4, three are available. The timershave their own motivating mechanism and clutch for engaging the sainewith the switch operators. The operation of each of the contacts orcircuits can be set vby the adjustment of the on detent or ofi detentwith respect to a timing scale shown on the face of the timer so thatthe timing action or circuit closing will occur ,at any desired intervalaccording to the setting of the on detent and will terminate at anydesired interval with relation to the time started. When the on detentis placed above the upper limit of the scale, its corresponding contactis closed when the timer is started or energized. If the oir detent isbelow the lower limit of the scale, its corresponding circuit, vafterhaving been closed according to the setting of the on detent, will stayclosed until the timer is deenergized or reset. One form of theMultiflex timermay be seen in U. S. Patent No. 2,175,864 issued October10, 1939. l

As an example of one type of suitable operat ing cycle, reference may bemade to Fig. 5, wherein a scale of minutes is shown in relation tovarious operations for bringing a polyphase induction motor having asynchronous speed of`1800 R. P M. up to 1500 R. P. M. It is understood,of course, that other speeds may be chosen and other intervals employed,the cycle shown being merely illustrative of one type of fast sugarcentrifuging cycle.

Assuming that the start button has just been depressed following aloading of the basket leaving the basket turning at about 200 R. P. M.,a period of 10 seconds is allowed before the motor windings are shiftedfrom low to high speed. It is assumed that the motor will reach a speedof aboutr450 R. P. M. during the 10 seconds. the end of about 40 secondsafter the shift to the high speed winding (50 seconds after starting thecycle), the motor will have reached the desired speed of 1500 R. P. M.,and at this time coasting switch PT1 is set to open so as to interruptthe driving action by de-energizing the motor and allowing thecentrifugal and motor to coast. It is to be understood that the time forreaching these various speeds will depend upon the size of motor,characteristics thereof, weight of charge in the centrifugal, and othervariables, but that these variables are relatively constant for anygiven conditions of use of a given machine.

The motor may be allowed to coast for 30 seconds and the washing, if itis to be used, may take place during this period, such not being shownor described herein as it does not constitute a part of this invention.At the end of the coasting period of 30 seconds, the regenerativebraking is started when switch PTz opens and can continue for l seconds,following which the regenerative braking is turned off by closing ofswitch CTa, whereupon the mechanical brake is set.

In Fig. 3, the settings of the control timer to correspond with theabove cycle of operations are shown schematically. The switch contactCTO is on from the beginning of the cycle and the off detent is arrangedso that it will openapproximately seconds before the end of the range ofthe control timer. The purpose of this is to de-energize the controltimer so that it cannot be left on indeterm-inately. The on detent ofCT1 is set for operation l0 seconds after the starting of the controltimer and serves to shift the driving motor from low to high speed inconjunction with the opening of C'Iz, the off detent of GT2 being set tooperate at the same time as, or immediately after, CT1 closes. Uponshift to the high speed winding, the control timer will be stoppedinasmuch as switch contact H211 is opened, but the timer will not reset.

The process timer of Fig. 4 also was started at the sam-e time as thecontr-o1 timer and runs continuously. Switch PTo is normally closedbefore the timer is started and the off detent thereof is setapproximately 5 seconds before the end of the 5 minute period for thepurpose of turning off the timer in a manner similar to the controltimer. Switch PTi is set to be on when the timer starts and to be openedat an appropriate time, say 50 seconds after starting the operation.This serves to cut oli' the power to the high speed winding andallow thecoasting to start. It is evident that the coasting switch PT1 may be setfor operation by the process timer a predetermined time interval inaccordance with the particular speed to be used. Switch PTz is set to beopened at a predetermined time after the coasting contact opens; in theparticular cycle shown, this interval being set for 30 seconds. Whenswitch PTz is opened, regenerative braking is started due tore-energization of the low speed solenoid. The control timer also isrestarted inasmuch as switch I|2a again is closed by the low speedsolenoid. The regenerative braking will be continued for an intervalgoverned by the setting of switch GT3, GT3 being arranged in theparticular cycle shown 10 seconds later than the position of the 01Tdetent of GT2. GT3 is arranged to close at the time interval requiredfor regenerative braking after operation of GT2. When CTs is closed, thecontrol timer will stop because the low speed winding is de-energizedand switch contact H2a opened.

All of the usual necessary adjustments can be made on the process timerbecause PT1 governs the length of time from the starting of the cycleuntil coasting starts and PTz governs the time of coasting. These twotimes can be adjusted as desired for the sugar involved.

In the event an electric drive is used with a hydraulic coupling, thetimer switches governing acceleration and coasting can be employed tocut oiT the supply of oil to the fluid coupling at the end of thepredetermined time necessary for the centrifugal to reach the desiredspeed. In Fig. 6, the motor 35 drives basket 35 through a iluid coupling3l, in a manner similar to that disclosed in the copending applicationof Joseph Hertrich, Serial No. 435,023, filed March 1'?, 1942, now U. S.Patent No. 2,441,356, or as disclosed in Fig. 1 of his copendingapplication Serial No. 713,329, filed November 30, 1946. The pump 38takes oil or fluid from tank 39 and delivers the same to the three-wayvalve 40. The three-way valve has pipe lil returning to the storage tank39 and pipe llZ leading to the coupling. The coupling continuouslydischarges oil. The control mechanism can be used to cut 01T the supplyof oil to the fluid coupling at the desired time, thus interruptingtorque transmission to the motor while allowing the driving motor tocontinue running under no load, by positioning the three-way valve toreturn the oil to the storage tank instead of supplying it into thecoupling. This may be done by using a three-way solenoid valve at l0with the solenoid connected in a control circuit like that of Fi 2 inthe relation occupied by relay solenoid Ill thereof. In such anembodiment, a single speed motor is used so that but one set of windingsand motor controls are provided in 'the position of said circuitoccupied bythe low speed windings, and the speed shifting and relatedcontrol timer elements thereof are eliminated.

The coasting control for a fluid coupling drive also can be used inconjunction with other types of controls for the uid coupling. Anexample of another type of control is one for the regulation of theaccelerating torque of the drive by control of the iluid supply to thecoupling in response to the torque reaction on the motor frame and anopposing control force, as disclosed in said copending applicationSerial No. 435,023. In a iiuid coupling drive, it is particularlydesirable to have a tachometer such as indicated at I3 to-shc'w the'-speedreached by the centrifugal basket, in= order to assist. inacicurately predetermining the desired setting for timer contact PT1.

Itis to be understood that the illustrated embodiments of thecombination and details'thereof may' be4 varied without4 departing fromthe spirit of theA invention except as defined 'inl th appended claims.

We claim:

l. In a suspended centrifugal machine adapted for operation to and froma high speed of rotation in each of frequently repeated cycles, thecombination of a basket-carrying spindle, a rotary driving systemconnected therewith to drive the same, said system including activatingmeans connected therewith shiftable to respective positions at whichsaid drive is inactive and is active to apply its full acceleratingtorque to said spindle, braking means normally inactive but movable toretard rotation of said spindle, control means including starting meansconnected with said activating means movable to shift the activatingmeans to said drive-active position upon actuation of the startingmeans, an adjustable timing system connected with said control means andsaid activating means started in action when said control means is movedso to shift said activating means, said timing system including a timerelement connected with said activating means acting as a predeterminedtime after starting the timing system to shift said activating means tosaid drive-inactive position, so that said spindle then may coast underits own momentum at a desired high centrifuging speed, and another timerelement connected with said braking means acting to move the same at apredetermined time after the action of the first-mentioned timerelement, so that said spindle is stopped after a period of coastingsufficient to complete the centrifuging at high speed.

2. In a suspended centrifugal machine adapted for operation to and froma high speed of rotation in each of frequently repeated cycles, thecombination of a basket-carrying spindle, a rotary driving systemconnected therewith having a full accelerating torque and speed whichdrive the spindle to more than a predetermined high centrifuging speed,said system including activating means connected therewith shiftable torespective positions at which said drive is inactive and is active toapply its full accelerating torque to said spindle, braking meansnormally inactive but movable to retard rotation of said spindle,control means including starting means connected with said activatingmeans movable to shift the same to said drive-active position uponactivation of the starting means, an adjustable timing system connectedwith said control means and moved thereby into action upon movement ofsaid control means to activate the driving system, said timing systemincluding a timer element connected with said activating means acting ata predetermined time after starting the timing system to shift saidactivating means to said drive-inactive position after a predeterminedperiod of application of said full accelerating torque, during whichsaid predetermined centrifuging speed is reached, so that said spindlethen may coast under its own momentum, and another timer elementconnected with said braking means acting to move the same at apredetermined time after the action of the first-mentioned timerelement, sol that saidi s'pindlef is' stopped after a periodik offcoasting; sufficient tocomplete the centrifuging at-highfspeedf Y A 3lin aususpendedi centrifugal machine-adapt"- ed for operation to andfrom a high speed of rotation in e'achyof frequently repeated cycles,the 4confibi'n'ation of a basket-carrying spindle, a rotary electricdriving motor directly connected with said spindle, said motor having afull accelerating.. torque ande speed which. drivev the spindle to morethan a predetermined higlr centrifuging speed, a power supply switchmechanism connected with said motor and shiftable to respectivepositions at which the motor is deenergized and is energized to applyits full accelerating torque to said spindle, braking means normallyinactive but movable to retard rotation of said spindle, control meansincluding a cycle starting element connected with said switch mechanismmovable to shift the same to said motor-energizing position When saidcycle starting element is activated, an adjustable timing systemconnected with said control means and moved into action upon movement ofsaid control means so to shift said switch mechanism, said timing systemincluding a timer element connected with said switch mechanism acting ata predetermined time after starting the timing system to shift saidswitch mechanism to said motor-deenergized position after apredetermined period of application of said full accelerating torque,during which predetermined high centrifuging speed is reached, so thatsaid spindle then may coast under its own momentum, and another timerelement connected with said braking means acting to move the same at apredetermined time after the action of the first-mentioned timerelement, so that the machine is stopped after a period of coastingsufficient to complete the centrifuging at high speed.

4. In a suspended centrifugal machine adapted for operation to and froma high speed of rotation in each of frequently repeated cycles, thecombination of a basket-carrying spindle, a rotary driving systemincluding an electric driving motor and a hydraulic coupling fortransmitting torque from said motor to said spindle, a power supplyswitch mechanism connected with said motor to energize the same andadapted normally to be left in motor-energizing position, lling controlmeans connected with said hydraulic coupling shiftable to respectivepositions at which the same is emptied and is lled to apply the fullaccelerating torque of said system to said spindle, braking meansnormally inactive ybut movable to retard rotation of said spindle,control means including a manually operable starting element connectedwith said filling control means movable to shift the same to saidcoupling-lled position upon activation of said starting element, anadjustable timing system connected with said manually operable controlmeans and moved thereby into action upon movement thereof so to shiftsaid filling control means, said timing system including a timer elementconnected with said lling control means acting at a predetermined timeafter starting the timing system to shift said iilling control means tosaid coupling-emptied position, so that said spindle may coast under itsown momentum, with said motor continuing energized and running, after apredetermined period of application of said full accelerating torqueimparting a desired high centrifuging speed, and another timer elementconnected with said braking means acting i1 to move the same at apredetermined time after UNITED STATES .PATENTS the action of thefirst-mentioned timer element, Number NameA 1 f Date so that saidspindle is stopped after a period of 1 866 499 n Hen. July 5, 1932.coasting sufficient to complete the centrifuging 2148320 Olcott Feb 211939 at high Speed 5 2152562 oloott s/Iar. '28 1939 RICHARD J- HUSER-2,175,864 Anderson oon. 1o, 1939 ANTHONY H- STUHLREYER- 2,280,916Johnson Apr. 28, 1942 REFERENCES CITED 2,338,053 Olcott Dec. 28, 1943The following references are of record in the 10 le of this patent:

